Resource provisioning is one of the main challenges in resource sharing environments such as multi-cluster Grids. In these environments each cluster serves requests from external (grid) users along with their own local users. The problem arises when there is not sufficient resources for local users (which have higher priority than grid users) to be served urgently. This problem could be solved by preempting resources from grid users and allocating them to the local users. However, resource preemption entails crucial side-effects such as decreasing resource utilization and increasing grid users' response time. Considering preemption side-effects, the question is that how the authors can minimize the number of preemptions taking place in a resource sharing environment.